U.S. Provisional Application No. 61/277,015, filed Sep. 18, 2009, is incorporated herein in their entirety by reference.
Most agricultural combines use a rotary threshing and/or separating system including at least one rotor drivingly rotated about a rotational axis within a rotor housing, the housing having a lower region including a perforated concave spaced radially outwardly of the rotor. The rotor will often have a frusto-conical inlet end having a helical flight or flights therearound for conveying a flow of crop material into the space between the rotor and the housing. The main body of the rotor will typically have an array or layout of threshing elements, most commonly including rasp bars and separating elements, particularly straight separator bars, which protrude radially outwardly therefrom into the space. The rasp bars and separator bars are configured differently, so as to perform different functions. The functions of the rasp bars include to cooperate with one or more vanes and guides typically disposed around the upper portion of the inner circumference of the rotor housing, for conveying a mat of the crop material along a generally helical path through the space, while cooperating with the vane or vanes and/or guides, and other aspects of the concave, e.g., bars, perforations and the like of the concave, to break up larger components of the crop material into its constituents, namely larger constituents or elements of crop residue commonly referred to as straw, which includes stalks, stems, cobs and the like, and smaller constituents which comprise the grain and smaller elements of material other than grain (MOG), in the well known manner.
Rasp bars are usually relatively narrow and generally concentrated nearer the inlet end of the rotor and include a plurality of serrations defining grooves in the threshing element. These grooves are oriented at small acute angles to, or generally aligned with, the direction of rotation of the rotor for raking or combing through the mat of crop material and uncoupling the smaller constituents from the crop material thus allowing the grain to fall through the openings in the concave. Straight separator bars, in contrast, are often longer and generally located nearer to the discharge end of the rotor and include one or more bars with at least one sharp edge extending perpendicular to the direction of rotation to plow the larger components of the crop mat and carry them away from the smaller grain and MOG.
To minimize damage to the grain it is desirable to separate the grain from the mat of crop material so it can fall through the openings in the concave as far forward in the threshing system as possible. The number and size of openings in the forward portion of the concave is limited, however, and it has been observed that some of the threshed grain travels over additional rasp bars or other threshing surfaces on the rotor prior to falling through an opening of the concave.
It has also been observed that when the relatively narrow rasp bars engage the mat of crop material, some of the larger portions, particularly ears of corn, will deflect off rather than flowing over the rasp bars. As a result the grain remains in the threshing system longer, encountering more threshing elements, risking damage to the grain, and increasing the likelihood that the cobs will break.
Accordingly, what is sought is a threshing system for an agricultural harvester including threshing elements which overcome at least one of the problems, shortcomings or disadvantages set forth above.